1. Field of the Invention
This invention relates to a method for the direct reduction of iron oxide materials, such as iron ore pellets, to solid metallic iron with a reducing gas.
2. Description of the Prior Art
Direct-reduction processes for iron manufacture have been spotlighted as small-scale iron manufacturing techniques, especially in developing countries.
Among them, known as the direct-reduction processes to be carried out in vertical shaft type furnaces are the Midrex process (e.g. U.S. Pat. Nos. 3,748,120, 3,764,123 and 3,617,227), the Armco process (e.g. U.S. Pat. Nos. 3,558,118 and 3,850,616) the Purofer process (e.g. U.S. Pat. Nos. 3,883,123 and 3,948,646), Nippon Steel Process (U.S. Pat. No. 4,001,010) and so forth.
In these processes, gases mainly composed of methane, such as a natural gas, are used for preparing gaseous reductants by reforming the gases in a reformer furnace. The reducing gases produced in the reformer furnace as a result of reactions involved in the reforming generally have relatively high temperatures exceeding 900.degree. C. which are too high for the gases to be blown into a reduction furnace, especially a vertical shaft type one. Therefore, in the prior art, the high-temperature gases produced in the reformer are subjected either to cooling and temperature control in a gas cooling apparatus or the like, or to cooling and temperature control by adding a cooled exhaust gas from the reduction furnace, for instance. It is a problem to be solved that the measures for the cooling and temperature control result in loss in the sensible heat of the reducing gas or in degradation of the reducing power of the reducing gas.